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Buying Guides for Backpacks


By Ian Perkins

Backpack Buying Guide


It’s time to hit the trail and you’re ready to buy a backpack. How do you know what to buy? First thing is first, the fit of a backpack can make or break your entire trip. It is crucial that you take your time and ensure that you are picking out the right pack. Don’t be afraid to try it on, load it up and walk around the store or the house before your trip to make sure that you have the perfect bag.


Backpack Capacity


The space inside the backpack or the backpack’s capacity is the volume of space available inside the backpack. A backpack is generally measured in liters, which can often be found in the pack’s name like the Osprey Ariel 65, a 65 liter pack. Sometime, however, backpack capacity will be measured in cubic inches. Many American outfitting companies will use a cubic inch capacity because of the varying design of backpacks. To simplify, 1 liter = approximately 61 cubic inches. While this number is being phased out, it is important to understand that whether the pack you’re looking for is listed in cubic inches or liters, those numbers are referencing the capacity of the backpack. We’ve included a table below to help you reference pack size.


A good tip for choosing the right backpack is NOT to overload your pack. Backpacks are designed to carry a specific range of weight, and when you overload your pack, or put too much in it, it will not perform to standard. Also, remember that when packing a backpack it is always best to pack everything on the inside of the backpack. When shopping for bags it is easy to imagine clipping and stringing gear to the outside of the bag via gear loops and lash straps. This is not ideal, however, because objects hanging on the outside will cause momentum displacement and make your backpack feel heavier. When in doubt, buy a bigger backpack.


To choose the correct backpack you have to figure out the duration of your trip. Are you heading out for 1-2 nights or maybe you are going for a 3-5 day trip? If you’re just starting out, think about the type of backpacking that you’re going to do, or ideally want to do the most of. Maybe you’ll do one or two quick weekend trips to learn, but ideally want to be doing 5-7 day trips once you’re comfortable. If that is the case, buy a bag for 5-7 day trips.



Trip Duration Pack Capacity (liters) Pack Capacity (cubic inches)
Day or Overnight (1 - 2 Nights) 16 -  45 1000 - 2700
Weekend (2 - 3 Nights) 50 - 65 3000 - 4000
Multi-day (3 - 5 Nights) 65 - 75 4000 - 4800
Extended (5+ Nights) 75 + 4800 +


Torso LengthMeasuring for a Backpack


When choosing your backpack you want to know your torso length NOT your height. You want to make sure your backpack is going to fit your frame properly nothing is more important than choosing a backpack according to your torso length. How do you determine your torso length?


Ask a pal for some assistance and locate the bone at the base of your neck, your C7 vertebra. The best way to go about doing this is to stand up straight with your feet shoulder width apart. Then drop your head to look at the ground. Have your buddy put his or her finger on the biggest bump on the back of your neck. Use a flexible tape measure and place your hands on your hips. You can figure this out by running your hands down the side of your rib cage until you come to the top of your hipbones. This is called the Iliac Crest. Reach your thumbs behind your back and have your friend measure from your C7 vertebra to the thumbs and that’s your torso length.


Pack Size Torso Length
Extra Small Up to 15 1/2"
Small 16" to 17 1/2"
Medium 18" to 19 1/2"
Large 20" +


Parts of your Backpack

Parts of a Backpack


Frame: The frame of the backpack is the most important part of your pack. Generally, the frame is comprised of two aluminum internal stays, as well as support stays. These stays act to distribute the weight of the framed backpack evenly over the surface of the pack. Most stays are designed to be removed and bent to custom fit to the contours of your body. Make sure that when purchasing a backpack, the stays are designed to carry the weight that you are expecting to encounter on your travels.


Hip-belt: The hip belt is crucial to the fit and carry of the backpack. When putting on a backpack you should always adjust and buckle the hip-belt before adjusting any other strap. The majority of the weight will be carried on this strap so it is important that it fits properly.


Shoulder Straps: The shoulder straps connect at the back of the pack and should wrap up and over the tops of your shoulders to help support the backpack. They should have adequate padding for the amount of weight you are planning to carry and should contour in agreement with your body. Be sure to get the proper fit with gender specific straps, women and men have different construction in the chest and shoulders and the straps are padded and shaped accordingly.

Parts of a Backpack 2


Sternum strap: Located around the mid-chest area this strap connects to your shoulder straps, which improves stability. This strap can be very helpful in uneven terrain. It simply helps to prevent the pack from shifting if you feel off-balance. It should be noted that this is a non-weight bearing strap so only pull it as tight as you need too. If you over tighten this strap it can cause the shoulder straps to sit improperly, producing rubbing or bruising.


Load-lifter straps: There are two sets of load-lifter straps on your backpack. One set connects the main body of the backpack to your shoulder straps, and the other connects the body of your backpack to your hip belt. These straps are crucial to the comfort and feel of a fully loaded backpack. They not only help in stabilizing the control of the backpack, but in balancing and shifting the weight. As you tighten these sets of straps, they move the weight respectively. Pulling the shoulder strap load lifters will bring the weight more on your shoulders, and pulling the hip belt lifters will move the weight closer to your hips. Note: It is possible to over tighten these straps. If either the shoulder straps or the hip belt are pulling off of your body due to the load lifters then they are over tightened.


Main Body: The main body of the backpack is comprised of two major parts: The “brain” and the “body.” The brain of the pack is upper flap used for quick access items while on the trail, and the body is the large access pocket underneath. The body of the pack is often divided into two parts, an upper part for the heaviest items, and a lower portion for softer items such as sleeping bags or cloths. You can learn about how to pack your backpack here.


Compression Straps: Compression straps are crucial to how the backpack carries. It is important to learn how to use them effectively in order to insure the comfort of the pack when fully loaded. When tightened, the compression straps will pull the weight closer to the frame of the backpack, making it feel lighter.


Finding the Perfect Fit


After you’ve narrowed down to your favorite backpack, it is important to make sure that it fits properly. Remember, backpacks are all about the right FIT, not the right style. Go ahead and load your backpack up with about 20 pounds of weight (we recommend using bags of rice, or a sack of potatoes).


Once you’ve got your bag on your back, the first strap you want to buckle is your hip-belt. Always, always, always, work the straps bottom to top when putting your backpack on. Buckle in this order: hip-belt, shoulder straps, sternum strap, and the finally, adjust the load lifters. Be sure not to over tighten anything. Your hip-belt should rest on your hips, giving downward and inward compression on your hips, with about 4 inches of webbing between the two pads. When tightening the hip-belt, be mindful to try and keep the buckle in the center, directly below your bellybutton. Next, to tighten the shoulder straps, locate the adjusters under your arms and pull down and behind you at the same time. The shoulder straps should be tight, but should allow you to move and breathe normally. Once you’ve adjusted the shoulder straps move to the sternum strap. The sternum strap should be parallel to the ground and cleanly out of the way of your neck line. Do not pull this strap tight, only taught, if it is over tightened it can pull the shoulder straps against the neck line and cause uncomfortable rubbing or bruising on the collar bones. Finally adjust the load-lifters on the pack. We recommend using two fingers and lightly pulling the adjusters tight until you’ve found the perfect balance. If either the shoulder straps or the hip belt are pulling off of the contours of the body, then you’ve over tightened the load lifters and may need to readjust.


Once you have all of the straps properly adjusted, spend some time walking around in your backpack. When walking, pay attention to the way the pack moves with your body, and how the straps feel. Make sure you have adequate circulation to your legs and arms, and that the shoulder and hip straps don’t cause unnecessary rubbing. (Note: while on the trail it is normal to have some bruising and irritation. Due to the amount of weight being carried, and the longevity of your trip, your backpack may cause general soreness, but shouldn't cause specific pain.)


Finally pay attention to the amount of contact that the backpack has with your back. As your walking, try to think about how much of your back is physically touching the pack, the more surface area in contact between your back and your pack the better it will feel when fully loaded. It can help to look at yourself in the mirror, if you see light between the bag and your back, you may need a different fit. (Note: don’t try to feel the contact with your hands. When you reach your arm backwards to touch your back you will create an artificial gap that may not exist when standing normally.) Finally don’t be afraid to try your backpack on a few times, or to jump back and forth between them, the better your new backpack fits, the more enjoyable your trip will be.

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